Climbers use active and passive clean protection devices for either protecting a climber in the event of a fall or for artificially supporting a climber's weight. Clean protection devices cam or wedge into a crack, groove, hole, or taper to support outward forces. Passive protection devices have no moving parts and typically wedge into constrictions to support outward forces. There are numerous types of passive protection devices including nuts, hexes, tri-cams, and chocks. Active protection devices contain at least two moving parts to enable a range of shapes and make it easier to insert and remove. Active camming devices are a subset of active protection devices and describe devices that use a retraction system to rotate two or more opposing camming lobes. The camming lobes are generally spring biased into an expanded position and are retracted with the retraction system to fit into different size cracks. Active camming devices are further divided into single axle and double axle devices. Single axle camming devices have a single central axle around which all camming lobes pivot. Double axle camming devices typically have two parallel axles on which opposing camming lobes pivot separately. Double axle devices are generally preferable because they have a much larger camming range.
The primary disadvantage of active camming devices is their considerable weight. For smaller camming devices, in particular, a large portion of the weight is in the connection system. The connection system connects the cam lobes to a clip-in point. The connection system usually consists of either a single or double stem connecting the cam head to the clip-in point. Double stem systems usually use a U-shaped wire rope for the stem, which creates a natural clip-in point at the end. Single stem systems are preferred because they are generally lighter and more flexible than double stem systems. For single stem systems, the clip-in point is usually either a loop formed in the wire rope or a separate part with an orifice that is either swaged or brazed to the single stem. The choice of a single or double stem system is independent of whether the camming device is a single or double axle device.
Retraction systems on active camming devices allow the climber to actuate the camming lobes from an expanded position to a retracted position. The difference of these two positions is called the camming range. Retraction systems generally consist of a trigger and flexible trigger wires that connect directly to the camming lobes. For smaller camming devices it is common for the trigger to be connected to a stem tube and then a yoke that is attached to the trigger wires. This configuration allows for stem compliance while reducing the chance of stem buckling. Trigger wires are typically situated between each set of two opposing cam lobes in camming devices with four camming lobes.
Larger active camming devices have several drawbacks. Larger camming devices must have longer stems to accommodate the larger camming lobes, and this leads to problems with stem buckling during retraction and increased stem weight. Retraction systems in larger cams do not utilize the benefits of a stem tube and yoke to prevent buckling because the trigger wires must clear the retracting camming lobes, and therefore must be nearly the same length as the stem. Larger active camming devices either use a single axle design or do not utilize the full benefit of the double axle design. In a double axle design, camming range increases as the distance between axles increases. Double axle designs do not realize the full benefit of camming range in larger camming devices because the axles must be placed relatively close to each other. The axles must be placed relatively close to each other to allow the trigger wires to wrap around the axles and remain in close proximity to the center of rotation of the camming lobe. In addition to reduced camming range, the other drawback of requiring the axles to be close to each other is that buckling of the camming lobes is a concern due to the unsupported length of each camming lobe. Single axle designs also have a long unsupported camming lobe length and therefore have the same camming lobe buckling concern. To prevent buckling, camming lobes in larger camming devices are made thicker, which adds weight.
A further drawback of larger camming devices is that they are bulky, particularly in their extended position. Climbers typically carry camming devices in their extended position because they are spring biased in this position and there is no practical method of locking them in a retracted position. It is desirable to carry larger camming devices in the retracted position because they are less bulky and also because they are less likely to snag on rock imperfections. Sometimes climbers will tie a camming device in the retracted position with a piece of cord but this is not very efficient and requires two hands to release.
Therefore, there is a need in the industry for larger camming devices that are lighter and have more camming range. There is also a need for larger camming devices to have a retraction locking mechanism that is easy to use and is deployable with one hand.